The objective of this proposal is to demonstrate the feasibility of a high trapping efficiency ion trap. This device can be used on ion trap based mass spectrometers including ion trap mass spectrometers (ITMS) and hybrid quadrupole ion trap time-of-flight mass spectrometers (QitTOF). The proposed ion trap will use a specially constructed split ring connected to a pair of matched RF voltage sources, to provide a quadrupole field that can be switched between 2D (linear trap) and 3D (Paul trap) modes electronically. Using the linear trap mode for trapping (injecting) ions, a projected 10 to 20 fold improvement in trapping efficiency can be achieved versus a 3D ion trap. After the ions are trapped and cooled inside the trap, the RF electronics can be switched back to the conventional 3D ion trap mode to scan and eject the ions. The trapping efficiency improvement would thus result in a significant improvement in sensitivity. The 3D scan and eject mode of this ion trap would provide a tight output ion beam, making for a simple interface to additional components such as a TOF MS or external fragmentation device. This configuration could be applied to current and future analytical instruments that use an ion trap, as well as to other ion trap applications, allowing one to take advantage of the best of both the 2D linear trap and the 3D Paul trap. Development of the proposed device could improve the performance of several analytical tools for proteomics research. For low abundant protein samples, it could provide much better sensitivity, with lower detection limits. The impact of ion trap technology development has been seen in many areas of life science research, and this proposed work should help continue this ion trap evolution. This work will not only benefit ion trap related mass spectrometer development, but will also expand our knowledge base of ion traps in general.